Q1 what must happen to hte liquid as it passes from the stomach to the small intestine for digestion to occur normally?
Q2 Can pepsin and trypsin function in the same environment? Explain?
2006-09-09 04:55:42 · 3 answers · asked by dancer 2 in Science & Mathematics ➔ Biology
DONT HAVE A BOOK YET THEY DIDNT COME IN.
2006-09-09 05:12:39 · update #1
Q1: The acid from the stomach must be neutralized.
The stomach is a strongly acidic environment; the sm. intestine is mildly alkaline. The stomach lining is especially suited to keep the acid from damaging the stomach; the sm. intestine lining is not. The acidic stomach contents must have its pH raised for digestion to continue normally (& to prevent internal harm!)
2006-09-09 05:04:10 · answer #1 · answered by WikiJo 6 · 0⤊ 0⤋
During a meal, secretion of gastric juices (containing HCl and pepsinogen) increases from a few mL / hour (the usual values between meals) to almost 1.5 L. HCl and pepsinogen secretion occurs on three phases:
Cephalic phase (yields about 1/5 of total secretion)
- Psychologic stimuli (such as anticipating a meal, its smell, sight and texture) start gastric secretion even before food reaches the stomach.
Gastric phase.
- The presence of partially-digested food (especially peptides and aminoacids) in the stomach promotes the secretion of the hormone gastrin. This peptide hormome acts on the stomech, thereby stimulating secretion. Histamine and acetylcholine also stimulate secretion, and all three factors act synergistically, so that their total potentiating effect is markedly higher than the sum of their individual contribuions. Therefore, blocking only one of this factors is enough to ellicit a substantial decrease of total secretion. Gastrin also increases gastric motility, leading to movement of the stomach contents (chyme) from the stomach and into the duodenum.
Enteric phase (yiels about 1/10 of total secretion):
- Duodenum pH is lowered by the arrival of (acidic) chyme. This increase in acidity stimulates the secretion of another hormone, secretin, which diminishes gastrointestinal motility and stops the transfer of chyme into the duodenum. Secretin acts on the stomach glands and inhibits HCl secretion. However, duodenum also secretes some gastrin, which counteracts this effect by stimulating HCl and pepsinogen secretion.
Secretin stimulates pancreas into secreting bicarbonate (HCO3-) into the duodenum. This anion neutralizes the hydrochloric acid just coming from the stomach, allowing duodenum pH to rise to the optimum values for the pancreatic enzymes (proteases, lipases, pancreatic amylase). These enzymes are secreted by the pancreas in response to cholecystokinin (CCK), a peptide hormone secreted by the duodenum when fatty acids are present in the chyme.
2006-09-09 05:07:26 · answer #2 · answered by OnionSkin 3 · 0⤊ 0⤋
Read your Biology book all the answer should be in the book as I tell my daughter read read read plz. read.
2006-09-09 05:00:20 · answer #3 · answered by busthead213 5 · 0⤊ 1⤋